The \(\alpha \) -Riesz kernels \(|x-y|^{\alpha -n}\)  of order \(\alpha \in (0,2]\) , \(\alpha <n\) , on \(\mathbb {R}^n\) , \(n\geqslant 2\)  (thus in particular the Newtonian kernel \(|x-y|^{2-n}\)  on \(\mathbb {R}^n\) , \(n\geqslant 3\) ), satisfy the energy and consistency principles as well as the first and second maximum principles [1]}. So do the associated \(\alpha \) -Green kernels on an arbitrary open subset of \(\mathbb {R}^n\) , \(n\geqslant 2\)  [2]}. The (2-)Green kernel on a planar Greenian set is likewise strictly positive definite [3]} and consistent [4]}, and it fulfills the first and second maximum principles (see [5]}, [3]}). Furthermore, all these kernels also satisfy the principle of positivity of mass (Theorem REF ).
